COVID-19 Infecting White Tail Deer To Create Transmission Danger

Animals transmit SARS-CoV-2 to humans. Humans then transmit it to other humans, while animals transmit it to other animals, or so some studies suggest. Then, there’s the danger of coronavirus mutating within an animal host and then reinfecting humans with a new variant, which is how some medical experts believe that the Omicron variant of COVID-19 came to spread among us. It had incubated in rats, who then infected humans.

Investigators with Penn State University found that one-third of white-tailed deer in their experiment tested positive for COIVD-19, most likely because of human-to-deer spillover and deer-to-deer transmission events. They published their findings on bioRxiv, a website that posts studies that have not yet been peer-reviewed.

“To help predict or prevent the emergence of the next pandemic and control infectious diseases with pandemic and panzootic potential, a better understanding of the human–animal molecular and ecological interface and its relevance to infection transmission dynamics is essential,” the study concludes. “Thus, we call for an urgent need to implement a more proactive and robust ‘One Health’ approach to better understand the ecology and evolution of SARS-CoV-2 in deer and other free-living species.”

One Health utilizes local, state, national, and global knowledge to pinpoint how people, plants, and animals influence health care outcomes. “Human populations are growing and expanding into new geographic areas,” says the Centers for Disease Control and Prevention on its One Health webpage. “As a result, more people live in close contact with wild and domestic animals, both livestock and pets. Animals play an important role in our lives, whether for food, fiber, livelihoods, travel, sport, education, or companionship. Close contact with animals and their environments provides more opportunities for diseases to pass between animals and people.”

This could be particularly problematic when it comes to trying to control COVID-19 spread and mutations, a point made by Kevin Kavanagh, MD, in a Q&A with Infection Control Today^® (ICT^®) last November. Talking about a study done by the US Department of Agriculture (DOA) on white-tail deer, Kavanagh—a member of ICT^®’s Editorial Advisory Board—said that “the deer apparently live with COVID-19 quite well, but, yet rapidly spread it amongst the herds. And that’s actually very problematic, because if it finds a host that it doesn’t make sick, but yet it can mutate and change and then reinfect other animals and plus mankind, that is one of the worrisome scenarios that could take place.”

White-tail deer are found in every state with the exception of Alaska, and are particularly prevalent in wooded areas in the northeast section of the United States, according to the DOA.

Penn State investigators found SARS-CoV-2 in 283 retropharyngeal lymph node (RPLN) samples from 151 free-living and 132 captive white-tailed deer in Iowa between September 2020 to January 2021.

“Ninety-four of the 283 deer (33.2%; 95% CI: 28, 38.9) samples were positive for SARS-CoV-2 RNA as assessed by RT-PCR,” the study states. “Notably, between November 23, 2020, and January 10, 2021, 80 of 97 (82.5%; 95% CI 73.7, 88.8) RPLN samples had detectable SARS-CoV-2 RNA by RT-PCR.”

The study states that the potential of species-to-species infection, while known, has rarely been studied. “Our study is the first to provide evidence of widespread dissemination of SARS-CoV-2 into any free-living species, in this instance, the white-tailed deer,” the study states. “While the precise route(s) of transmission of SARS-Cov-2 from humans to deer are unknown, there are several ways in which deer may be exposed to the virus from humans, including through feeding in backyards or even when a susceptible deer may come in contact with potentially infectious material saliva, urine, etc.) from an infected human in forested areas or exurban environments.”

Deer can also be exposed to SARS-CoV-2 through infected fomites, wastewater, or other infected animals. They can then become what the investigators call reservoir hosts.

“A reservoir host can facilitate viral evolution and the emergence of lineages with increased virulence for the original host,” the study states. “Since many animal species already harbor an extensive array of endemic endogenous CoVs, the presence of a free-living reservoir host for SARS-CoV-2 may provide an opportunity for the virus to recombine and acquire or evolve increased fitness traits such as increased virulence, transmissibility, pathogenicity, and immune evasion.”